Degradation of Flame-Retardant Cross-Linked Polyethylene Caused by Heat, Gamma-Rays, and Steam

Various kinds of polymers are used for electrical insulation in nuclear power plants. They are subjected to thermal and radioactive stresses, depending on their locations. They are also subjected to high-temperature steam in the event of an accident. Regarding this, sheets of flame-retardant cross-linked polyethylene (FR-XLPE) were subjected to heat, gamma-rays, and steam exposure, and their infrared absorption spectra, stress-strain relations, indenter moduli, and permittivity spectra were measured. As a result, we have made clear various degradation-induced property changes of FR-XLPE. In addition, it has also become clear that cross-linked structures are formed by the gamma-ray irradiation in FR-XLPE. In this regard, some aspects of degradation due to subsequent steam exposure are suppressed by the formation of firm three-dimensional cross-linked structures.